JPH0420268B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] The present invention relates to a resin-sealed semiconductor device that is sealed with a cured product of an epoxy resin composition and has high reliability in terms of moisture resistance and high-temperature electrical properties. [Technical background of the invention and its problems] Epoxy resin has excellent electrical properties, mechanical properties, chemical resistance, etc., and is therefore widely used as a highly reliable electrical insulating material for encapsulating semiconductor devices. Recently, in place of conventional hermetic sealing using ceramics, most semiconductor devices such as integrated circuits, large-scale integrated circuits, transistors,
Diodes and other components are sealed using an epoxy resin composition for low-pressure molding. As epoxy resin compositions for semiconductor encapsulation, epoxy resins,
Epoxy resin compositions comprising novolac type phenolic resin curing agents, imidazole curing accelerators, etc. are widely used. However, resin-sealed semiconductor devices obtained by transfer molding using conventional epoxy sealing resins have the following drawbacks. (1) Moisture resistance is inferior to the high level of reliability required for resin-encapsulated semiconductor devices. (2) High temperature resistance is inferior to the high level of reliability required for resin-encapsulated semiconductor devices. First, to explain the moisture resistance mentioned above, resin-sealed semiconductor devices are sometimes used or stored in high-temperature, high-humidity environments, so reliability must be guaranteed even under such conditions. No. As an evaluation test for quality assurance of moisture resistance, 85℃
Alternatively, an accelerated evaluation method in which the material is exposed to saturated steam at 120°C has been used, and recently, a bias application type evaluation test in which a voltage is applied to further improve acceleration has also been conducted. However, since the cured product of the encapsulated epoxy resin composition is hygroscopic and moisture permeable, under such high temperature and high humidity conditions, moisture from the outside may penetrate into the interior through the cured epoxy resin layer, or the seal may deteriorate. It enters the interior through the interface between the stopper resin and the lead frame and reaches the surface of the semiconductor element. Therefore, as a result of the action of this moisture and impurity ions existing in the sealing resin, resin-sealed semiconductor devices suffer from defects mainly due to decreased insulation, increased leakage current, and corrosion of aluminum electrodes, wiring, etc. cause an accident. Further, when a bias voltage is applied, defects due to corrosion of aluminum electrodes and wiring occur particularly frequently due to its electrochemical action. Therefore, conventional epoxy resin-encapsulated semiconductor devices are not fully satisfactory with respect to the above-mentioned moisture resistance, and there has been a demand for improved moisture resistance. Next, electric characteristics at high temperatures will be explained. Since resin-sealed semiconductor devices are sometimes used under high temperature conditions, reliability must be guaranteed even under such conditions. A typical evaluation test for this purpose is an accelerated test in which reliability is evaluated by applying a bias voltage at 80°C to 150°C. It is well known that in such tests, a phenomenon in which leakage current increases due to channeling occurs particularly frequently in devices with MOS structures with sensitive surfaces or devices with PN junctions to which reverse bias is applied. There is. This phenomenon is thought to occur when an electric field acts on the resin layer that is in contact with the surface of the element to which a voltage is applied. Conventional epoxy resin-sealed semiconductor devices are not fully satisfactory with respect to the above-mentioned electrical characteristics at high temperatures, and improvements have been sought. [Object of the Invention] The object of the present invention is to improve the drawbacks of such conventional epoxy resin-encapsulated semiconductor devices,
An object of the present invention is to provide a highly reliable epoxy resin-encapsulated semiconductor device that is encapsulated with an epoxy resin composition having a novel composition and has excellent moisture resistance and high-temperature electrical characteristics. [Summary of the Invention] As a result of intensive research aimed at achieving the above object, the present inventors have discovered that imidazole, etc., which are conventionally used as curing accelerators, are the main cause of the above drawbacks. . Then, they discovered that the moisture resistance and high-temperature electrical characteristics of semiconductor devices could be improved by using the following epoxy resin composition as a molding material for a resin body that encapsulates a semiconductor, and they were able to complete the present invention. Ivy. That is, the resin-sealed semiconductor device of the present invention is a resin-sealed semiconductor device comprising a semiconductor element and an epoxy resin molded body covering the semiconductor element, wherein the epoxy resin molded body has ( a) an epoxy resin, (b) an epoxy resin curing agent or/and an acid anhydride curing agent having at least two phenolic hydroxyl groups in one molecule, and (c) a reaction mixture of an organophosphine compound and an organoaluminum compound. It is characterized by being a cured product of an epoxy resin composition containing the following. Note that the resin molded body as used in the present invention refers to a cured product of the epoxy resin composition according to the present invention. The epoxy resin used in the present invention may be any resin as long as it is generally used as an epoxy resin. Examples of such epoxy resins include glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, phenol volak type epoxy resin, and cresol novolak type epoxy resin; glycidyl ester type epoxy resin; glycidyl amine type epoxy resin; Aliphatic epoxy resins; alicyclic epoxy resins; heterocyclic epoxy resins; epoxy resins having two or more epoxy groups in one molecule such as halogenated epoxy resins, and one or more selected from the group consisting of these; Two or more types are used. The above epoxy resin has a low chloride ion content.
It is preferable that the content of hydrolyzable chlorine is 10 ppm or less and 0.1% by weight or less. Furthermore, as the epoxy resin, it is preferable to use a glycidyl ether type epoxy resin, and in particular, it is most preferable to use a novolak type epoxy resin having an epoxy equivalent of 170 to 300 because a cured product with excellent properties can be obtained. . The curing agents for epoxy resins having two or more phenolic hydroxyl groups in one molecule used in the present invention include phenolic resins, polyoxystyrenes, and polyphenol compounds, and specific examples include phenolic hydroxyl groups. Novolak-type phenolic resins such as lactic resin, cresol novolak resin, tert-butylphenol novolak resin, and nonylphenol novolak resin; resol-type phenolic resin; polyoxystyrene such as polyparaoxystyrene; and bisphenol A
and the like, as well as halides of these compounds. Among these, novolak type phenolic resins and polyoxystyrene are most preferred. Further, these curing agents can be used alone or in a mixed system in which two or more of them are appropriately combined. The acid anhydride that can be used in the present invention may be any aliphatic, alicyclic or aromatic carboxylic anhydride or a substituted carboxylic anhydride thereof. Examples of such acid anhydrides include maleic anhydride, succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride,
Hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, nadic anhydride (3,
6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride), methylnadic anhydride, 3,
Examples include 3'-4,4'-benzophenonetetracarboxylic anhydride, tetrabromophthalic anhydride, chlorendic anhydride, and one or more selected from the group consisting of these. These curing agents may be used alone or in an appropriate combination. The amount of the curing agent to be blended is preferably such that the ratio of the total number of phenolic hydroxyl groups and/or anhydrous carboxyl groups to the number of epoxy groups in the epoxy resin is within the range of 0.5 to 1.5. The reason for this is that outside the above range, the moisture resistance of the resulting epoxy resin composition tends to deteriorate. In the epoxy resin composition according to the present invention, what is used as the third component is a reaction mixture of an organic phosphine compound and an organic aluminum compound, which can be easily obtained by mixing the two. First, the organic phosphine compound has the following general formula: (In the formula, R ₁ , R ₂ and R ₃ may be the same or different, and each has an alkyl group having 1 to 40 carbon atoms; a phenyl group; an allyl group such as a tolyl group; a cyclohexyl group) represents a cycloalkyl group or hydrogen atom such as (except when R ₁ , R ₂ and R ₃ are all hydrogen atoms), such as triphenylphosphine, tributylphosphine, tricyclohexyl Tertiary phosphine compounds such as phosphine, tritolylphosphine and tribenzylphosphine, secondary phosphine compounds such as diphenylphosphine and butylphenylphosphine, and primary phosphine compounds such as phenylphosphine and octylphosphine. One or more types selected from the group consisting of these are used. Among these, tertiary phosphine is preferred, and triarylphosphine such as triphenylphosphine is particularly preferred. Next, as an organoaluminum compound, the following general formula: (In the formula, R ₄ , R ₅ and R ₆ may be the same or different, and include an alkyl group having 1 to 40 carbon atoms; an aryl group such as a phenyl group; a tolyl group; a cyclohexyl group, etc.) represents a cycloalkyl group, hydrogen atom or halogen atom, etc. However,
Except when R ₄ , R ₅ and R ₆ are all hydrogen atoms or halogen atoms. ), such as trimethylaluminum, triethylaluminum, tributylaluminum, tricyclopropylaluminum, triphenylaluminum, tritolylaluminum, tribenzylaluminum, dimethylphenylaluminum, diphenyl(phenylethynyl)aluminum, diethyl Examples include bromoaluminum, diethylaluminum hydride, diphenylaluminum hydride, dimethylaluminum hydride, and one or more selected from the group consisting of these. Particularly preferred is triphenylaluminum. It is believed that when these organic phosphine compounds and organic aluminum compounds are mixed, they easily react to form a coordination compound. In the present invention, an equimolar reaction mixture of both is most preferred, but it is not necessarily an equimolar reaction mixture of both. Usually, it is preferable that the amount of the organoaluminum compound is 1 mol or less per 1 mol of the organic phosphine compound. The amount of the above reaction mixture according to the present invention is:
0.001 for the total amount of epoxy resin and hardener
It is preferable to blend within the range of ~20% by weight,
More preferably, it is 0.01 to 10% by weight. Melt mixtures can be used in the present invention. The molten mixture consists of three aspects: (1) reaction mixture and epoxy resin, (2) reaction mixture and curing agent, and (3) reaction mixture, epoxy resin and curing agent. These are used by melt-mixing them in advance and mixing them with other components during the production of the sealing composition. It is preferable to blend an inorganic filler into the epoxy resin composition of the present invention as necessary, and especially in the case of transfer molding of semiconductor elements such as integrated circuits and transistors, it is preferable to blend an inorganic filler. preferable. One reason for this is to improve moldability, and another reason is to reduce the difference in thermal expansion coefficient between the parts to be sealed, such as elements, bonding wires, and lead frames, and the sealing resin. This is to reduce defects such as wire breakage that occur due to a large difference in thermal expansion coefficients. Examples of inorganic fillers used include quartz glass powder, crystalline silica powder, glass fiber, talc, alumina powder, calcium silicate powder, calcium carbonate powder, barium sulfate powder, and magnesia powder. Powder and crystalline silica powder are most preferred in terms of high purity and low coefficient of thermal expansion. The blending amount of these inorganic fillers varies depending on the type of epoxy resin, curing agent, and inorganic filler, but for example, when used for transfer molding, the weight ratio is 1.5 times the total amount of epoxy resin and curing agent. ~4 times is sufficient. Regarding the particle size distribution of the inorganic filler, moldability can be improved by making the distribution uniform by combining coarse particles and fine particles. The epoxy resin composition according to the present invention may be used, as necessary, with release agents such as natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, or paraffins, chlorinated paraffin, bromine, etc. Flame retardants such as toluene, hexabromobenzene and antimony trioxide, coloring agents such as carbon black, silane coupling agents, etc. may be appropriately added and blended. A general method for preparing the epoxy resin composition according to the present invention as a molding material is to thoroughly mix the raw material components selected to have a predetermined composition using, for example, a mixer, and then melt-mix them using heated rolls. Alternatively, an epoxy resin molding material can be easily obtained by adding a mixing treatment using a kneader or the like. The resin-sealed semiconductor device of the present invention can be easily manufactured by sealing the semiconductor device using the above-mentioned epoxy resin composition or molding material. The most common method of sealing is low-pressure transfer molding, but injection molding,
Sealing by compression molding, casting, etc. is also possible. As a special sealing method, a sealing method in which a semiconductor surface is coated using a solvent-based or non-solvent-type composition, and a local sealing application as so-called juncture coating can also be used. The epoxy resin composition or molding material is heated and cured during sealing, and finally a resin-sealed semiconductor device can be obtained which is sealed with the cured product of this composition or molding material. . During curing, it is desirable to heat to 150°C or higher. The semiconductor device in the present invention includes an integrated circuit, a large-scale integrated circuit, a transistor, a thyristor, a diode, etc., and is not particularly limited. In the following, the present invention will be explained in more detail with reference to Examples. [Examples of the Invention] Synthesis Example 1 1 mol of triphenylphosphine was dissolved in toluene, and 1 mol of triphenylaluminum was gradually added under a nitrogen stream while cooling to cause a reaction.
Toluene was removed to obtain a reaction mixture (I). Synthesis Example 2 1 mol of triphenylphosphine was dissolved in toluene, and the solution was gradually added to 1 mol of triethylaluminum under a nitrogen stream while cooling to cause a reaction. Toluene was removed to obtain a reaction mixture. 5 parts by weight of this reaction mixture and 90 parts by weight of phenyl novolak resin with a molecular weight of 800 were mixed and heated to form a molten mixture.
I got (1). Synthesis Example 3 1 mol of triphenylphosphine was dissolved in toluene, and 0.5 mol of triisobutylaluminum was gradually added under a nitrogen stream while cooling to cause a reaction. Toluene was removed to obtain a reaction mixture. Five parts by weight of this reaction mixture and 90 parts by weight of a phenol novolac resin having a molecular weight of 800 were mixed and heated to obtain a molten mixture (2). Example 1 A cresol novolac type epoxy resin (epoxy resin A) with an epoxy equivalent of 220 and a brominated epoxy novolac resin (epoxy resin B) with an epoxy equivalent of 290 were used as the epoxy resins; a phenol novolac resin (molecular weight: 800) was used as the curing agent. )of;
and triphenylphosphine (1 mol) and triphenylaluminum (1 mol) as reaction mixture.
In addition, quartz glass powder (filler), antimony trioxide (flame retardant), carnauba wax (mold release agent), carbon black (coloring agent), and silane coupling agent (V -glycidoxypropyltrimethoxysilane), an epoxy resin composition was prepared according to the formulation (parts by weight) shown in Table 1. Example 2 5 parts by weight of a reaction mixture of triphenylphosphine (1 mol) and triethylaluminum (1 mol) as a molten mixture (1) of reaction mixture and curing agent were added to 90 parts by weight of a phenolic novolak resin having a molecular weight of 800. The formulation shown in Table 1 (parts by weight) using the same ingredients as in Example 1 except that the melt-mixed one was used.
An epoxy resin composition was prepared. Example. 3. As a molten mixture (2) of reaction mixture and curing agent, 5 parts by weight of a reaction mixture of triphenylphosphine (1 mol) and triisobutylaluminum (0.5 mol) were added to a phenol novolac resin 90 with a molecular weight of 800.
In addition to using parts by weight and melt-mixed,
An epoxy resin composition was prepared using the same ingredients as in Example 1 and the formulation (parts by weight) shown in Table 1. Example 4 Example 1 except that phenol novolak resin and tetrahydrophthalic anhydride were used as the curing agent.
An epoxy resin composition was prepared using the same ingredients as shown in Table 1 (parts by weight). Comparative Example 1 Except for the curing agent in Example 1, the rest was as in Example 1.
An epoxy resin composition was prepared using the same ingredients as shown in Table 1 (parts by weight). Comparative Example 2 Example 1 except that triphenylphosphine was used instead of reaction mixture (I) in Example 1.
An epoxy resin composition was prepared using the same ingredients as shown in Table 1 (parts by weight). Comparative Example 3 Example 1 except that 2-methylimidazole was used instead of reaction mixture (I) in Example 1.
An epoxy resin composition was prepared using the same ingredients as shown in Table 1 (parts by weight). Comparative Example 4 Example 1 except that 2-methylimidazole was used in place of the reaction mixture (I) in Example 1, and tetrahydrophthalic anhydride was further used as a curing agent.
An epoxy resin composition was prepared using the same ingredients as shown in Table 1 (parts by weight).

[Table] The epoxy resin compositions were mixed using a mixer and then kneaded using heated rolls to obtain a molding material. Transfer molding was performed using the molding material thus obtained, and a MOS type integrated circuit was sealed with resin. For sealing, mold the molding material heated to 90℃ with a high-frequency preheater at 195℃ for 4 minutes, and
This was done by after-curing at 180°C for 8 hours. According to the above method, 100 resin-sealed semiconductor devices were manufactured using each epoxy resin composition, and the following tests were conducted. (1) Moisture resistance test (PCT): 10V was applied in water vapor at 120°C and 2 atm, and the cumulative failure rate (%) of defective products whose aluminum wiring broke due to corrosion was investigated over time. (2) MOS-BT test: Apply a drain voltage of 5V and an offset gate voltage of 5V to the offset gate MOS FET circuit in an oven at 100℃, and when the leakage current value increases to more than 100 times the initial value. were considered to be defective, and the cumulative defective rate (%) of defective products that occurred was investigated over time. Table 2 shows the results of the moisture resistance test, and Table 3 shows the results of the MOS-BT test to investigate high-temperature electrical characteristics.

【table】

【table】

〔Effect of the invention〕

As is clear from the table, in the epoxy resin-encapsulated semiconductor device sealed using the epoxy resin composition of the present invention, corrosion of aluminum wiring, etc. is greatly reduced, and there is no occurrence of defects due to increased leakage current. It has extremely excellent moisture resistance and high-temperature electrical properties, and is of great industrial value.

Claims (1)

[Scope of Claims] 1. A resin-encapsulated semiconductor device comprising a semiconductor element and an epoxy resin encapsulant covering the semiconductor element, wherein the epoxy resin encapsulant comprises (a) an epoxy resin; b) an epoxy resin curing agent or/and an acid anhydride curing agent having at least two phenyl hydroxyl groups in one molecule; and (c) an epoxy resin composition comprising a reaction mixture of an organophosphine compound and an organoaluminum compound. An epoxy resin-encapsulated semiconductor device characterized by being a cured product. 2. The epoxy resin-encapsulated semiconductor device according to claim 1, wherein the epoxy resin is a novolak type epoxy resin having an epoxy equivalent of 170 to 300. 3. The epoxy resin-encapsulated semiconductor device according to claim 1, wherein the epoxy resin curing agent is a novolak type phenolic resin. 4. The epoxy resin-encapsulated semiconductor device according to claim 1, wherein the reaction mixture is an equimolar reaction mixture of the organic phosphine compound and the organic aluminum compound. 5. Claim 1, wherein the epoxy resin sealing body uses a molten mixture of the reaction mixture, the epoxy resin, or/and the curing agent.
The epoxy resin sealed semiconductor device described above. 6. The epoxy resin sealed semiconductor device according to claim 1, wherein the epoxy resin sealed body contains an inorganic filler.